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Roger E. Summons - One of the best experts on this subject based on the ideXlab platform.
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Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals.
Nature ecology & evolution, 2018Co-Authors: J. Alex Zumberge, Gordon D. Love, Paco Cárdenas, Erik A. Sperling, Sunithi Gunasekera, Megan Rohrssen, Emmanuelle Grosjean, John P. Grotzinger, Roger E. SummonsAbstract:Sterane biomarkers preserved in ancient sedimentary rocks hold promise for tracking the diversification and ecological expansion of eukaryotes. The earliest proposed animal biomarkers from demosponges (Demospongiae) are recorded in a sequence around 100 Myr long of Neoproterozoic-Cambrian marine sedimentary strata from the Huqf Supergroup, South Oman Salt Basin. This C30 Sterane biomarker, informally known as 24-isopropylcholestane (24-ipc), possesses the same carbon skeleton as sterols found in some modern-day demosponges. However, this evidence is controversial because 24-ipc is not exclusive to demosponges since 24-ipc sterols are found in trace amounts in some pelagophyte algae. Here, we report a new fossil Sterane biomarker that co-occurs with 24-ipc in a suite of late Neoproterozoic-Cambrian sedimentary rocks and oils, which possesses a rare hydrocarbon skeleton that is uniquely found within extant demosponge taxa. This Sterane is informally designated as 26-methylstigmastane (26-mes), reflecting the very unusual methylation at the terminus of the steroid side chain. It is the first animal-specific Sterane marker detected in the geological record that can be unambiguously linked to precursor sterols only reported from extant demosponges. These new findings strongly suggest that demosponges, and hence multicellular animals, were prominent in some late Neoproterozoic marine environments at least extending back to the Cryogenian period.
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Paleoproterozoic sterol biosynthesis and the rise of oxygen
Nature, 2017Co-Authors: David A. Gold, Abigail M. Caron, Gregory P. Fournier, Roger E. SummonsAbstract:Natural products preserved in the geological record can function as ‘molecular fossils’, providing insight into organisms and physiologies that existed in the deep past. One important group of molecular fossils is the steroidal hydrocarbons (Steranes), which are the diagenetic remains of sterol lipids. Complex sterols with modified side chains are unique to eukaryotes, although simpler sterols can also be synthesized by a few bacteria. Sterol biosynthesis is an oxygen-intensive process; thus, the presence of complex Steranes in ancient rocks not only signals the presence of eukaryotes, but also aerobic metabolic processes. In 1999, Steranes were reported in 2.7 billion year (Gyr)-old rocks from the Pilbara Craton in Australia, suggesting a long delay between photosynthetic oxygen production and its accumulation in the atmosphere (also known as the Great Oxidation Event) 2.45–2.32 Gyr ago. However, the recent reappraisal and rejection of these Steranes as contaminants pushes the oldest reported Steranes forward to around 1.64 Gyr ago (ref. 6). Here we use a molecular clock approach to improve constraints on the evolution of sterol biosynthesis. We infer that stem eukaryotes shared functionally modern sterol biosynthesis genes with bacteria via horizontal gene transfer. Comparing multiple molecular clock analyses, we find that the maximum marginal probability for the divergence time of bacterial and eukaryal sterol biosynthesis genes is around 2.31 Gyr ago, concurrent with the most recent geochemical evidence for the Great Oxidation Event. Our results therefore indicate that simple sterol biosynthesis existed well before the diversification of living eukaryotes, substantially predating the oldest detected Sterane biomarkers (approximately 1.64 Gyr ago), and furthermore, that the evolutionary history of sterol biosynthesis is tied to the first widespread availability of molecular oxygen in the ocean–atmosphere system.
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Prospects for Sterane Preservation in Sponge Fossils from Museum Collections and the Utility of Sponge Biomarkers for Molecular Clocks
Bulletin of the Peabody Museum of Natural History, 2016Co-Authors: David A. Gold, Shane S. O'reilly, Genming Luo, Derek E. G. Briggs, Roger E. SummonsAbstract:Abstract The sponge biomarker hypothesis argues that 24-isopropylcholestanes preserved in Neoproterozoic-age rocks are “molecular fossils” left behind by marine sponges. Despite genetic and geologic support for this hypothesis, 24-isopropylcholestane has never been reported from a sponge body fossil. This lack of direct evidence regarding the source of sponge biomarkers through deep time leaves unanswered questions, such as whether their biosynthesis evolved once in sponges or multiple times across different lineages. In this study, we analyzed 10 sponge fossils from the Yale Peabody Museum of Natural History collections in pursuit of evidence of Sterane biomarkers. We failed to recover 24-isopropylcholestane and instead found a near-identical Sterane profile across all samples. This result indicates a combination of little to no Sterane preservation in the fossils themselves, coupled with anthropogenic hydrocarbon contamination during their collection and storage. However, signals from bacterial biomarke...
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Sterols in red and green algae: quantification, phylogeny, and relevance for the interpretation of geologic Steranes.
Geobiology, 2008Co-Authors: Robin B. Kodner, Roger E. Summons, Ann Pearson, Andrew H. KnollAbstract:Steroids, a class of triterpenoid lipids with high preservation potential, are widely distributed in sedimentary rocks. All eukaryotes have a physiological requirement for these molecules, making steroids important biomarkers for aiding our understanding of eukaryote molecular evolution and geologic history. C(26)-C(30) sterols are the molecules most commonly incorporated or synthesized by eukaryotes, and correspond to C(26)-C(30) Steranes ubiquitously and abundantly preserved in petroleums and sedimentary bitumens. Because these sterols occur in evolutionarily diverse taxa, it can be difficult to associate any particular compound with a single group of organisms. Nevertheless, geochemists have still been able to draw parallels between the empirical patterns in geologic Sterane abundances and the age of petroleum source rocks. Paleobiologists have also used Sterane data, in particular the patterns in C(29) and C(28) Steranes, to support fossil evidence of an early radiation of green algae in latest Proterozoic and Paleozoic and the succession of the major modern phytoplankton groups in the Mesozoic. Although C(29) sterols are found in many eukaryotes, organisms that produce them in proportional abundances comparable to those preserved in Proterozoic and Paleozoic rocks are limited. Based on a large, phylogenetically based survey of sterol profiles from the kingdom Plantae, we conclude that modern ulvophyte and early diverging prasinophyte green algae produce high abundances of C(29) relative to C(27) and C(28) sterols most consistent with the Sterane profiles observed in Paleozoic rocks. Our analysis also suggests that ancestral stem groups among the Plantae, including the glaucocystophytes and early divergent red algae are also plausible candidates.
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Thermal maturity of the 1. 05 Ga Nonesuch Formation, North American Midcontinent rift: Biomarker ratios and hopane and Sterane stereoisomers
AAPG Bulletin, 1991Co-Authors: G.b. Hieshima, Lisa M. Pratt, Roger E. SummonsAbstract:Differences in the apparent level of thermal maturity indicated by Sterane and hopane stereoisomers arise from the relationship between time and temperature in the maturation process. As part of a continuing study of the approximately 1.05 Ga Nonesuch Formation, North American Midcontinent Rift. The authors have evaluated the thermal maturity of organic matter based on biomarker distributions and ratios of stereoisomers (17 samples). Steranes and hopanes, once thought to be absent from Nonesuch bitumen and petroleum, have been identified and quantified by multiple-reaction-monitoring gas chromatography mass spectrometry. Other indicators of thermal maturity including the methylphenanthrene index and the ratio of {alpha}{alpha}{alpha}/{alpha}{alpha}{alpha} + {alpha}{beta}{beta} Steranes are covariant with the 20S/20S + 20R ratio of C{sub 29} Sterane. The ratios of pristane/nC{sub 17}, phytane/nC{sub 18}, and trisnorhopane/trisnorneohopane (Ts/Tm) are not covariant with the 20S/20S + 20R ratio of C{sub 29} Sterane. The ratios of pristane/nC{sub 17}, phytane/nC{sub 18}, and trisnorhopane/trisnorneohopane (Ts/Tm) are not covariant with the 20S/20S + 20R ratio of C{sub 29} Sterane reflecting control by the source of organic matter. The long burial history of the Nonesuch has influenced the kinetic transformations of hopane and Sterane stereoisomers to a greater extent than thermal influence. The 22S/22S + 22R ratio ofmore » C{sub 31} hopane equilibrates more rapidly than the C{sub 29} 20S/20S + 20R ratio even at relatively low burial temperatures given sufficient geologic time. The Nonesuch Formation is moderately mature with respect to petroleum formation and preservation despite a billion year long burial history.« less
David A. Gold - One of the best experts on this subject based on the ideXlab platform.
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Paleoproterozoic sterol biosynthesis and the rise of oxygen
Nature, 2017Co-Authors: David A. Gold, Abigail M. Caron, Gregory P. Fournier, Roger E. SummonsAbstract:Natural products preserved in the geological record can function as ‘molecular fossils’, providing insight into organisms and physiologies that existed in the deep past. One important group of molecular fossils is the steroidal hydrocarbons (Steranes), which are the diagenetic remains of sterol lipids. Complex sterols with modified side chains are unique to eukaryotes, although simpler sterols can also be synthesized by a few bacteria. Sterol biosynthesis is an oxygen-intensive process; thus, the presence of complex Steranes in ancient rocks not only signals the presence of eukaryotes, but also aerobic metabolic processes. In 1999, Steranes were reported in 2.7 billion year (Gyr)-old rocks from the Pilbara Craton in Australia, suggesting a long delay between photosynthetic oxygen production and its accumulation in the atmosphere (also known as the Great Oxidation Event) 2.45–2.32 Gyr ago. However, the recent reappraisal and rejection of these Steranes as contaminants pushes the oldest reported Steranes forward to around 1.64 Gyr ago (ref. 6). Here we use a molecular clock approach to improve constraints on the evolution of sterol biosynthesis. We infer that stem eukaryotes shared functionally modern sterol biosynthesis genes with bacteria via horizontal gene transfer. Comparing multiple molecular clock analyses, we find that the maximum marginal probability for the divergence time of bacterial and eukaryal sterol biosynthesis genes is around 2.31 Gyr ago, concurrent with the most recent geochemical evidence for the Great Oxidation Event. Our results therefore indicate that simple sterol biosynthesis existed well before the diversification of living eukaryotes, substantially predating the oldest detected Sterane biomarkers (approximately 1.64 Gyr ago), and furthermore, that the evolutionary history of sterol biosynthesis is tied to the first widespread availability of molecular oxygen in the ocean–atmosphere system.
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Prospects for Sterane Preservation in Sponge Fossils from Museum Collections and the Utility of Sponge Biomarkers for Molecular Clocks
Bulletin of the Peabody Museum of Natural History, 2016Co-Authors: David A. Gold, Shane S. O'reilly, Genming Luo, Derek E. G. Briggs, Roger E. SummonsAbstract:Abstract The sponge biomarker hypothesis argues that 24-isopropylcholestanes preserved in Neoproterozoic-age rocks are “molecular fossils” left behind by marine sponges. Despite genetic and geologic support for this hypothesis, 24-isopropylcholestane has never been reported from a sponge body fossil. This lack of direct evidence regarding the source of sponge biomarkers through deep time leaves unanswered questions, such as whether their biosynthesis evolved once in sponges or multiple times across different lineages. In this study, we analyzed 10 sponge fossils from the Yale Peabody Museum of Natural History collections in pursuit of evidence of Sterane biomarkers. We failed to recover 24-isopropylcholestane and instead found a near-identical Sterane profile across all samples. This result indicates a combination of little to no Sterane preservation in the fossils themselves, coupled with anthropogenic hydrocarbon contamination during their collection and storage. However, signals from bacterial biomarke...
Gordon D. Love - One of the best experts on this subject based on the ideXlab platform.
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Free and kerogen-bound biomarkers from late Tonian sedimentary rocks record abundant eukaryotes in mid-Neoproterozoic marine communities.
Geobiology, 2019Co-Authors: J. Alex Zumberge, Don Rocher, Gordon D. LoveAbstract:Lipid biomarker assemblages preserved within the bitumen and kerogen phases of sedimentary rocks from the ca. 780-729 Ma Chuar and Visingsö Groups facilitate paleoenvironmental reconstructions and reveal fundamental aspects of emerging mid-Neoproterozoic marine communities. The Chuar and Visingsö Groups were deposited offshore of two distinct paleocontinents (Laurentia and Baltica, respectively) during the Tonian Period, and the rock samples used had not undergone excessive metamorphism. The major polycyclic alkane biomarkers detected in the rock bitumens and kerogen hydropyrolysates consist of tricyclic terpanes, hopanes, methylhopanes, and Steranes. Major features of the biomarker assemblages include detectable and significant contribution from eukaryotes, encompassing the first robust occurrences of kerogen-bound regular Steranes from Tonian rocks, including 21-norcholestane, 27-norcholestane, cholestane, ergostane, and cryostane, along with a novel unidentified C30 Sterane series from our least thermally mature Chuar Group samples. Appreciable values for the Sterane/hopane (S/H) ratio are found for both the free and kerogen-bound biomarker pools for both the Chuar Group rocks (S/H between 0.09 and 1.26) and the Visingsö Group samples (S/H between 0.03 and 0.37). The more organic-rich rock samples generally yield higher S/H ratios than for organic-lean substrates, which suggests a marine nutrient control on eukaryotic abundance relative to bacteria. A C27 Sterane (cholestane) predominance among total C26 -C30 Steranes is a common feature found for all samples investigated, with lower amounts of C28 Steranes (ergostane and crysotane) also present. No traces of known ancient C30 Sterane compounds; including 24-isopropylcholestanes, 24-n-propylcholestanes, or 26-methylstigmastanes, are detectable in any of these pre-Sturtian rocks. These biomarker characteristics support the view that the Tonian Period was a key interval in the history of life on our planet since it marked the transition from a bacterially dominated marine biosphere to an ocean system which became progressively enriched with eukaryotes. The eukaryotic source organisms likely encompassed photosynthetic primary producers, marking a rise in red algae, and consumers in a revamped trophic structure predating the Sturtian glaciation.
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Demosponge steroid biomarker 26-methylstigmastane provides evidence for Neoproterozoic animals.
Nature ecology & evolution, 2018Co-Authors: J. Alex Zumberge, Gordon D. Love, Paco Cárdenas, Erik A. Sperling, Sunithi Gunasekera, Megan Rohrssen, Emmanuelle Grosjean, John P. Grotzinger, Roger E. SummonsAbstract:Sterane biomarkers preserved in ancient sedimentary rocks hold promise for tracking the diversification and ecological expansion of eukaryotes. The earliest proposed animal biomarkers from demosponges (Demospongiae) are recorded in a sequence around 100 Myr long of Neoproterozoic-Cambrian marine sedimentary strata from the Huqf Supergroup, South Oman Salt Basin. This C30 Sterane biomarker, informally known as 24-isopropylcholestane (24-ipc), possesses the same carbon skeleton as sterols found in some modern-day demosponges. However, this evidence is controversial because 24-ipc is not exclusive to demosponges since 24-ipc sterols are found in trace amounts in some pelagophyte algae. Here, we report a new fossil Sterane biomarker that co-occurs with 24-ipc in a suite of late Neoproterozoic-Cambrian sedimentary rocks and oils, which possesses a rare hydrocarbon skeleton that is uniquely found within extant demosponge taxa. This Sterane is informally designated as 26-methylstigmastane (26-mes), reflecting the very unusual methylation at the terminus of the steroid side chain. It is the first animal-specific Sterane marker detected in the geological record that can be unambiguously linked to precursor sterols only reported from extant demosponges. These new findings strongly suggest that demosponges, and hence multicellular animals, were prominent in some late Neoproterozoic marine environments at least extending back to the Cryogenian period.
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Scarcity of the C30 Sterane biomarker, 24-n-propylcholestane, in Lower Paleozoic marine paleoenvironments
Organic Geochemistry, 2015Co-Authors: Megan Rohrssen, Benjamin C. Gill, Gordon D. LoveAbstract:Abstract 24-n-Propylcholestane (24-npc), a C30 Sterane compound derived from sterol precursors which are the major sterol constituents of modern pelagophyte microalgae, occurs in certain Neoproterozoic rocks and oils and throughout the Phanerozoic rock record. This broad distribution leads 24-npc to be widely considered a reliable indicator of open to partially restricted marine depositional conditions for source rocks and oils. Here we report two significant hiatuses in the occurrences of 24-npc in the Lower Paleozoic marine rock record: the first in the Middle–Late Cambrian and the second in the Late Ordovician–early Silurian transition for a range of lithofacies (carbonates and siliciclastic rocks), organic carbon contents (both organic-lean and organic-rich), and paleoceanographic environments (shelf and deeper water marine settings) and observed offshore of two paleocontinents, Laurentia and Baltica. The Ordovician–Silurian gap is at least 9 million years, and possibly up to 20 million years, in duration. Robust older occurrences of 24-npc Steranes in some Neoproterozoic rocks and oils suggest that oceanographic conditions in our intervals of Lower Paleozoic time were unfavorable for the proliferation of pelagophyte algae as phytoplankton. Caution should therefore be applied when interpreting a lacustrine versus marine depositional environmental setting for source rocks and oils in these intervals of Early Paleozoic time using lipid biomarker assemblages.
Guoying Sheng - One of the best experts on this subject based on the ideXlab platform.
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Identification of C24 and C25 lanostanes in Tertiary sulfur rich crude oils from the Jinxian Sag, Bohai Bay Basin, Northern China
Organic Geochemistry, 2011Co-Authors: Guoying Sheng, Ping'an PengAbstract:Abstract Unusual short chain lanostanes (C 24 and C 25 ) and C 30 lanostane were identified in sulfur rich crude oils from the Jinxian Sag, Bohai Bay Basin, northern China. Besides the regular Steranes (C 27–30 ), a series of 4-methyl Steranes (C 22−23 , C 27−30 ), 4,4-dimethyl Steranes (C 22−24 , C 28−30 ), short chain Steranes (C 23−26 ), abundant pregnanes (C 21−22 ) and androstanes (C 19−20 ), together with sulfur containing steroids (20-thienylpregnanes and thienylandrostanes) were detected in the aliphatic and branched-cyclic hydrocarbon fraction of these crude oils. A literature survey of some long chain Sterane analogues (e.g., A-nor-Steranes, norcholestanes, C 30 Steranes, lanostanes) and pregnanes seems to point to a sponge and/or dinoflagellate source. 4-Methyl, 4,4-dimethyl steroids and lanosterols (4,4,14-trimethyl steroids as the basic skeleton of lanostanes) can be derived from methanotrophic bacteria. Thus, a biological origin from a prokaryotic methylotroph can be used to explain the common source of abundant short chain Steranes (C 23–26 ), 4-methyl (C 22–23 ) and 4,4-dimethyl Steranes (C 22–24 ), as well as lanostanes (C 24–25 and C 30 analogues) in our oil samples. Generally, the steroids appear to have been extensively sulfurized with sulfur substitution at the C-22 position in the side chain during the early stage of diagenesis, which was readily subject to attack by bacterial degradation (enzymatic cleavage) and/or abiotic oxidation. As a consequence, short chain Sterane analogues (e.g., abundant pregnanes and androstanes in this study) and short chain lanostanes (C 24 −C 25 ) might later be released through cleavage of weak C–S bonds at the C-22 carbon in the sulfurized steroids and lanostane sulfides. Finally, the formation of the short chain C 24 −C 25 lanostanes and distinctive occurrence of short chain Steranes in this study can be well explained by microbial biodegradation of sulfurized lanostanoids and steroids in the reservoir.
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Triterpane and Sterane biomarkers in the YA13-1 condensates from Qiongdongnan Basin, South China Sea
Chemical Geology, 2003Co-Authors: Yi Zhou, Ansong Geng, Guoying Sheng, Junhong Chen, Yongqiang Xiong, Qiming ZhangAbstract:Triterpanes and Steranes in condensates from the YA13-1 gas field, Qiongdongnan Basin, were monitored. The YA13-1 condensates have unusual biomarker distributions dominated by terpanes and Steranes derived from higher plants. Anomalously abundant 1 got-oleanane and remarkably abundant bicadinanes are present in the YA13-1 condensates, whereas the 17alpha-hopane contents are extremely low. Taraxastane and significantly abundant 17alpha-diahopanes occur in the condensates. In addition, a number of unknown C-29 and C-30 pentacyclic triterpanes including previously unreported compounds were detected in the condensates, some of which are significantly abundant. The unknown compounds may be terrestrial biomarkers. C-29 homologues are relatively predominant among the regular and rearranged Steranes. The diaSterane concentrations are markedly higher than those of regular Steranes. The maturity of the YA13-1 condensates is relatively high, at the peak to late oil generation stage (corresponding to 0.85-1.10% Ro), based on Sterane and terpane and including bicadinane maturity parameters (i.e. T/(T-1 + R) and 2T/R bicadinane ratios). The above maturity assessment result is different from that based on diamondoid maturity parameters (%Ro = 1.60-1.70) [Org. Geochem. 25 (1996) 179], which can be explained by a contribution of hydrocarbons from two sources at different depths. The YA13-1 condensates were probably generated from the Yacheng and Lingshui coal-bearing source rocks buried both in the Qiongdongnan Basin (3400-5000 m) and in the Yinggehai Basin (>5000 m). The possible contribution of lower maturity hydrocarbons from the Yacheng and Lingshui Formations (3400-4100 m) in the Qiongdongnan Basin to the YA13-1 gases and condensates should not be neglected. (C) 2003 Elsevier Science B.V. All rights reserved.
Stuart Batterman - One of the best experts on this subject based on the ideXlab platform.
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PAHs, nitro‐PAHs, hopanes, and Steranes in lake trout from Lake Michigan
Environmental toxicology and chemistry, 2014Co-Authors: Lei Huang, Sergei M Chernyak, Stuart BattermanAbstract:The present study examines concentrations and risks of polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), Steranes, and hopanes in lake trout collected in Lake Michigan. A total of 74 fish were collected in 2 seasons at 3 offshore sites. The total PAH concentration (Σ9 PAH) in whole fish ranged from 223 pg/g to 1704 pg/g wet weight, and PAH concentrations and profiles were similar across season, site, and sex. The total NPAH (Σ9 NPAH) concentrations ranged from 0.2 pg/g to 31 pg/g wet weight, and carcinogenic compounds, including 1-nitropyrene and 6-nitrochrysene, were detected. In the fall, NPAH concentrations were low at the Illinois site (0.2-0.5 pg/g wet wt), and site profiles differed considerably; in the spring, concentrations and profiles were similar across sites, possibly reflecting changes in fish behavior. In the fall, the total Sterane (Σ5 Sterane) and total hopane (Σ2 Hopane) levels reached 808 pg/g and 141 pg/g wet weight, respectively, but concentrations in the spring were 10 times lower. Concentrations in eggs (fall only) were on the same order of magnitude as those in whole fish. These results demonstrate the presence of target semivolatile organic compounds in a top predator fish, and are consistent with PAH biodilution observed previously. Using the available toxicity information for PAHs and NPAHs, the expected cancer risk from consumption of lake trout sampled are low. However, NPAHs contributed a significant portion of the toxic equivalencies in some samples. The present study provides the first measurements of NPAHs in freshwater fish, and results suggest that additional assessment is warranted.
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PAHs, nitro‐PAHs, hopanes, and Steranes in lake trout from Lake Michigan
Environmental toxicology and chemistry, 2014Co-Authors: Lei Huang, Sergei M Chernyak, Stuart BattermanAbstract:The present study examines concentrations and risks of polycyclic aromatic hydrocarbons (PAHs), nitro-PAHs (NPAHs), Steranes, and hopanes in lake trout collected in Lake Michigan. A total of 74 fish were collected in 2 seasons at 3 offshore sites. The total PAH concentration (S9PAH) in whole fish ranged from 223pg/g to 1704pg/g wet weight, and PAH concentrations and profiles were similar across season, site, and sex. The total NPAH (S9NPAH) concentrations ranged from 0.2pg/g to 31pg/g wet weight, and carcinogenic compounds, including 1-nitropyrene and 6-nitrochrysene, were detected. In the fall, NPAH concentrations were low at the Illinois site (0.2-0.5pg/g wet wt), and site profiles differed considerably; in the spring, concentrations and profiles were similar across sites, possibly reflecting changes in fish behavior. In the fall, the total Sterane (S5Sterane) and total hopane (S2Hopane) levels reached 808pg/g and 141pg/g wet weight, respectively, but concentrations in the spring were 10 times lower. Concentrations in eggs (fall only) were on the same order of magnitude as those in whole fish. These results demonstrate the presence of target semivolatile organic compounds in a top predator fish, and are consistent with PAH biodilution observed previously. Using the available toxicity information for PAHs and NPAHs, the expected cancer risk from consumption of lake trout sampled are low. However, NPAHs contributed a significant portion of the toxic equivalencies in some samples. The present study provides the first measurements of NPAHs in freshwater fish, and results suggest that additional assessment is warranted. Environ Toxicol Chem 2014;33:1792-1801. # 2014 SETAC
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pahs polycyclic aromatic hydrocarbons nitro pahs and hopane and Sterane biomarkers in sediments of southern lake michigan usa
Science of The Total Environment, 2014Co-Authors: Lei Huang, Sergei M Chernyak, Stuart BattermanAbstract:Abstract PAHs in the Great Lakes basin are of concern due to their toxicity and persistence in bottom sediments. Their nitro derivatives, nitro-PAHs (NPAHs), which can have stronger carcinogenic and mutagenic activity than parent PAHs, may follow similar transport routes and also are accumulated in sediments. Limited information exists regarding the current distribution, trends and loadings of these compounds, especially NPAHs, in Lake Michigan sediments. This study characterizes PAHs, NPAHs, and biomarkers Steranes and hopanes in surface sediments collected at 24 offshore sites in southern Lake Michigan. The ΣPAH 14 (sum of 14 compounds) ranged from 213 to 1291 ng/g dry weight (dw) across the sites, levels that are 2 to 10 times lower than those reported 20 to 30 years earlier. Compared to consensus-based sediment quality guidelines, PAH concentrations suggest very low risk to benthic organisms. The ΣNPAH 5 concentration ranged from 2.9 to 18.6 ng/g dw, and included carcinogenic compounds 1-nitropyrene and 6-nitrochrysene. ΣSterane 6 and ΣHopane 5 concentrations ranged from 6.2 to 36 and 98 to 355 ng/g dw, respectively. Based on these concentrations, Lake Michigan is approximately receiving 11, 0.16, 0.25 and 3.6 metric tons per year (t/yr) of ΣPAH 14 , ΣNPAH 5 , ΣSterane 6 and ΣHopane 5 , respectively. Maps of OC-adjusted concentrations display that concentrations decline with increasing off-shore distance. The major sources of PAHs and NPAHs are pyrogenic in nature, based on diagnostic ratios. Using chemical mass balance models, sources were apportioned to emissions from diesel engines (56 ± 18%), coal power plants (27 ± 14%), coal-tar pavement sealants (16 ± 11%), and coke ovens (7 ± 12%). The biomarkers identify a combination of petrogenic and biogenic sources, with the southern end of the lake more impacted by petroleum. This first report of NPAH levels in sediments of Lake Michigan reveals several carcinogenic compounds at modest concentrations, and a need for further work to assess potential risks to aquatic organisms.
